Donald Trump shakes hands at the Iowa State Fair on Aug. 15 in Des Moines. Trump has tapped into a feeling among many Republicans that the nation has become, as he put it, “an economic wasteland.” (Charles Ommanney/The Washington Post)

The way Joe McCoy sees it, the last time America was great was when Ronald Reagan was president, when people played by the rules. No, it was in the ’70s, Holly Martin says, when you could depend on Americans to work hard. No, to find true American greatness, Steve Trivett contends, you need to go back to before the Vietnam War, “when you could still own a home and have a good job even if you didn’t have a college education.”

Even if they don’t have “Make America Great Again” campaign caps, Donald Trump’s supporters easily recite the signature slogan of the real estate developer’s insurgent presidential bid. And even if they don’t agree on exactly why the country lost its way, they do accept — give or take a few degrees of hyperbole — Trump’s contention that the United States has become, as he has put it, “an economic wasteland” that is “committing cultural suicide.”

The premise behind “Make America Great Again” is that the country is no longer great. It can be great again, and the campaign has a certain can-do billionaire in mind as the guy to make that happen, but at the moment, the leading contender for the nomination of the party that regularly touts the notion of American exceptionalism is arguing that the country ain’t what it used to be.

Interviews with Trump supporters across the country find a profusion of perspectives on how and when America lost its mojo; what bonds them is a sense of frustration so abiding that they’re willing to take a chance on a man they readily admit is anything but presidential, at least the way the term has historically been defined.

“The way he talks is just silly sometimes — he sounds like a fourth-grader,” said Holly Martin, a freelance technology writer who recently moved, in search of a lower cost of living, from the suburbs of Washington to the exurban town of Winchester, Va. But Martin, 59, attended a training session for Trump campaign volunteers recently because “he talks like a regular guy, and he actually loves this country. He’s not afraid to say that we’ve lost our good character.”

Many Trump supporters interpret their candidate’s rough rhetoric not as anger, but as determination. Without ever having seen Trump’s reality TV show, “The Apprentice,” Martin has come to think that he has a rare ability to get things done. She was a Republican all her life — until her party regained the majority in Congress in 2014 and proceeded, she said, “to do nothing. They did nothing on Obamacare, nothing on cutting spending, nothing on restoring honesty. They hate us, so now I’m done with Republicans. Trump is not one of them. He doesn’t hate us. He really believes we can make America great again, and I’m not an optimistic person, but I think he can, because he’s got a built-in ability to use the media, just like Obama.”

For some supporters, especially those in the second half of life, Trump’s slogan is a tribute to a simpler time. “He could have said, ‘Make America what it was before’ and I would have voted for him,” said Jane Cimbal, 69, who lives in Winchester and signed up to collect signatures to get Trump on the Virginia ballot. “The last time we had good jobs and respect for the military and law enforcement was, oh, probably during Eisenhower.”

Cimbal doesn’t view Trump as an optimist of the Reagan stripe, but she’s okay with voting for a harsh critic. “He speaks his mind,” she said. “So many of the others are wishy-washy. Mr. Trump isn’t a provocateur to annoy people but to get them thinking.”

Cimbal, a loyal Republican, wants people to think about how to curb illegal immigration and protect Second Amendment gun ownership rights, but she’s mainly drawn to Trump because she thinks his plain talk can get things done. Her goal is to restore a time “when there wasn’t as much animosity toward each other, when everything wasn’t about race and people just got along.”

The crowds at Trump events tend to be older and whiter than the national population, but so is the party whose nomination he seeks, and so are frequent voters generally. If younger supporters don’t have firsthand experience of the Eisenhower, Kennedy or Reagan years, they nonetheless share the older generation’s sense of loss.

Joe McCoy, who is 31, says he started out this campaign season “laughing at this Trump guy like everyone else.”

Still, the more he heard Trump, the more the greatness slogan resonated. “He boasts a lot, he’s got trophy wives, he’s not exactly Mr. Clean, so I was skeptical,” said McCoy, who lives in Norwich, Conn., where he does tech support from home for a multinational company.

“Mitt Romney was more my kind of guy: practical, a nice guy. But you know, people don’t like a nice guy. They like this guy because he’s right about us losing our country. I really don’t think we should be letting kids go into whichever bathroom they want to in school. The Democrats are really reaching too far on the social issues. And there’s no retirement anymore, no pensions.”

McCoy laments the pervasive sense that it no longer pays to play by the rules. That’s where immigration enters the equation: “When my wife came here from the Philippines, she had to go through a health assessment, background checks and interviews to become a citizen. Now, these people come in from Mexico and Central America through some mule, just whoever comes.”

“I’m not a rigid tea partyer,” he continued. “I’m in favor of government paying for roads and the fire department. Social Security is a great thing. But I don’t think Trump is really much of a conservative; he’s definitely more moderate than the others.”

McCoy recognizes that his sense of lost greatness is probably different from that of others who are drawn to Trump, but he says that’s all right. When Trump talks about losing the country, “it’s about whatever you want it to be,” McCoy said. “He lets you fill in the blanks.”

That free-floating sense of decline expresses itself in many different ways among Trump supporters. Some speak of a fading sense of mobility, a loss of the expectation that each generation will surpass its parents’ standard of living. Others focus on the loss of blue-collar jobs and a sense that only those with computer backgrounds can take advantage of the new digital economy.

Although Trump has said in campaign speeches that he came up with his slogan himself, Ronald Reagan put “Let’s Make America Great Again” on buttons and posters in his 1980 campaign, and John Kennedy used “We Can Do Better” and “Get This Country Moving Again” as slogans in 1960.

But Reagan and Kennedy were widely perceived as happy warriors with a shining vision of what the country could be. Reagan and Kennedy couched their laments for America’s perceived loss of prowess amid a larger promise of change — ideological in Reagan’s case and generational in Kennedy’s. Other successful candidates carefully grounded their critiques of the country’s state in optimistic packaging. “There is nothing wrong with America that cannot be cured by what is right with America,” Bill Clinton said in his first inaugural address in 1993.

“A lot of the difference is tonal,” said David Greenberg, a historian of the presidency at Rutgers University. “Kennedy had great confidence and self-possession, and although Reagan’s optimism has been overstated, he got the balance right between that shining personality and his tough, no-compromise willingness to stand up to the Iranians, the Soviet Union or the liberals. There wasn’t just the tone of anger and resentment, the shouting people down, that you see with Trump.”

In this past week’s GOP debate, Sen. Marco Rubio (Fla.) pointedly presented a more optimistic perspective, rejecting the developer’s blunt, blustery barbs about the nation’s decline. “Our greatest days lie ahead,” Rubio said.

Undaunted, Trump began his closing statement with one of his trademark lines: “Our country doesn’t win anymore.” It’s a theme he has developed in several of his books, including a new 2016 campaign edition of “Time to Get Tough!,” where he writes: “The country I love is a total economic disaster right now. We have become a laughingstock, the world’s whipping boy, blamed for everything, credited for nothing, given no respect. You see and feel it all around you, and so do I.”

That dark view of the nation would seem to violate the political science adage that Americans favor optimistic candidates, but Trump’s dire summation of the state of the nation is far from unique in the annals of presidential campaigns.

“In the ’30s in the Depression, many people felt the American way of life was finished,” said Robert Lieber, a government professor at Georgetown University who wrote a book arguing against the notion that the country is in decline. “In 1957, after Sputnik, there was a strong belief that the Soviets were much more disciplined than us. Since the ’70s, it’s been the Russians who were eating our lunch and then the Japanese and then the Chinese. Each time, we underestimated America’s material strengths.”

Lieber sees Trump’s slogan as a symbol of his ability to slice through standard political rhetoric: “His discourse is deliberately provocative, but he’s refreshing to a lot of people because he talks about reality with the bark off, and people are sick to death of the language of political correctness.”

Steve Trivett, sports editor of a newspaper in central Florida, worries about his six grandchildren’s futures “in an anything-goes society where there are no ramifications for any action. People here are concerned about why nothing gets done. We’re not angry, we’re frustrated. And then Donald Trump comes along and says, ‘I am going to make America great again’ and we all go, ‘Hallelujah!’ ”

Trivett, who turns 70 this month, is still working because he says he “blew my 401(k) sending two kids to college, and I don’t regret it, but where’s the security? When America was great, our economy was strong. Our economy’s been shipped off to other countries. Can Donald Trump solve that? Hell, I don’t know. Somebody not as flamboyant or egomaniacal might be more effective, but I’m not sure anybody can bring us back. At least Trump gets things done. The last Democrat I voted for was Jimmy Carter. He was a good, honest man, and the system ate him up. So maybe we need a guy like Trump.”